1. Field of the Invention
The present invention relates to a color filter for use in a CCD camera, various display elements such as liquid crystal display element, display panel, color image sensor, method and apparatus for manufacturing the color filter, and a liquid crystal display element using the color filter.
2. Description of the Related Art
Color filter manufacturing methods which are known at present include (1) dyeing method, (2) pigment dispersing method, (3) printing method, (4) ink-jet method, and (5) electrodeposition method.
According to the first method of dyeing, a water soluble polymer layer for dyeing is formed on a glass substrate and is patterned in a desired shape by photolithography. After that, the layer is soaked in a dye solution, thereby obtaining a colored pattern. By repeating the process three times, color filter layers of red (R), green (G), and blue (B) are obtained. Since hues are rich, transmittance is high, and the degree of completion of the technique is high, the color filter layers are used in many charge-coupled devices (CCD) at present. Since a dye is used; however, light resistance is low and the number of fabricating processes is large. As a method of fabricating the color filter for a liquid crystal display element (LCD), the pigment dispersing method is replacing the dyeing method.
According to the second method of pigment dispersion, a resin layer in which a pigment is dispersed is formed on a glass substrate and is patterned by photolithography. The process is repeated three times to thereby obtain color filter layers of R, G, and B. The fabricating method has drawbacks of a large number of processes and high cost.
According to the third method of printing, a pigment is dispersed in a thermosetting resin, colors of R, G, and B are applied by repeating printing three times, and the resin is set by being heated, thereby obtaining color filter layers. Although this method does not require photolithography for the RGB layer forming process, the method has drawbacks of low resolution and unevenness in film thickness.
According to the fourth method of ink jet, an ink-receiving layer is formed first, a desired pattern is formed and is made hydrophilic and hydrophobic, ink is jetted to hydrophilic areas to thereby obtain a color filter layer. Although the method also does not require photolithography, there is a drawback that the resolution is low. Since colors are often mixed between neighboring filter layers, the positional accuracy is also low.
According to the fifth method of electrodeposition, in an electrolyte obtained by dispersing a pigment in water soluble polymer, a high voltage of about 100 V is applied to a transparent electrode which is preliminarily patterned to form an electrodeposition film. By repeating the process three times, color filter layers of RGB are obtained. In the method, the electrode is preliminarily patterned by photolithography and is used as an electrode for electrodeposition. There is consequently a drawback that the pattern shape is limited and the color filter layer cannot be used for a TFT liquid crystal.
Generally, a color filter in which only color filter layers are formed cannot be used for a liquid crystal. It is necessary to cover the gaps between filter cells of the colors with a black matrix. Usually, photolithography is used to form the black matrix and it is one of major factors of high costs.
A method of manufacturing a color filter with a high resolution and excellent pattern accuracy by a simple process at low costs without performing a complicated process such as photolithography is desired. In recent years, a display capable of displaying video information and communication information with a high resolution has been being demanded more and more. A color filter that is patterned with a higher resolution is accordingly being demanded.
On the other hand, in a liquid crystal display (LCD) for displaying an image by using liquid crystal molecules, a color filter and a transparent substrate are disposed so as to face each other via a sealing material and a liquid crystal layer is formed between them. In order to display an image by controlling the alignment of the liquid crystal molecules in the liquid crystal layer, a drive electrode for controlling the alignment of the liquid crystal molecules has to be provided on the side where the color filter is disposed in the liquid crystal layer. Since the color filter layer is generally insulating, however, a conductive layer is indispensable between the liquid crystal layer and the color filter, and the layer has to be separately provided and used as a drive electrode.
In the color filter manufacturing process, therefore, a process for forming the conductive layer is added after the color filter layer is formed. It is, however, difficult to make the color filter layer itself uniformly and highly conductive in order to omit the process. Under present circumstances, a conductive color filter with a simple construction is not yet provided.
The present invention has been made in view of the above circumstances and realizes the following.
The invention provides a conductive color filter manufacturing method for easily manufacturing a conductive color filter having a fine, complicated pixel pattern, with high surface smoothness and a high resolution, and having high and uniform conductivity to enable the alignment of the liquid crystal molecules to be accurately controlled.
The invention also provides an apparatus for manufacturing a simple-structured conductive color filter having a conductive color filter layer with a high resolution at low cost by using the method.
The invention also provides a color filter having a uniform and high conductivity, which can be directly used in a liquid crystal display element without providing a conductive layer on a color filter layer formed.
Further, the invention provides a liquid crystal display element which uses a conductive color filter with a high resolution having a uniform and high conductivity that enables the alignment of the liquid crystal molecules to be accurately controlled, and which uses a light-transmitting conductive film as a component of the color filter as a drive electrode for liquid crystal display.
A part that solves the problems is as follows.
The present invention provides a method of manufacturing a conductive color filter, includes: a step of selectively forming a black matrix on a light-transmitting photoconductive thin film of a light-transmitting substrate on which a light-transmitting conductive film and the photoconductive thin film having a function of generating a photovoltaic force are stacked in this order; and a step of allowing at least the photoconductive thin film of the substrate to be in contact with an electrolyte including a conductive electrodeposition material containing a colorant, irradiating the photoconductive thin film with light, selectively making a light-irradiated area of the photoconductive thin film generate a photovoltaic force, and electrochemically depositing the electrodeposition material to thereby form a conductive colored electrodeposition film.
The electrodeposition material may contain a compound having a carboxyl group.
The compound having the carboxyl group may be a polymer having a hydrophobic group and a hydrophilic group and the number of hydrophobic groups may be 40 to 80% of the total number of the hydrophobic and hydrophilic groups.
The polymer may be a random copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group.
In the conductive color filter manufacturing method, 50% or more of the number of hydrophilic groups of the polymer can change from a water-soluble state to a water-insoluble state or reversibly from a water-insoluble state to a water-soluble state in accordance with a change in pH.
In the conductive color filter manufacturing method, the electrodeposition material may contain a light-transmitting conductive material.
In the conductive color filter manufacturing method, the coloring material may be a conductive colorant, which can control alignment of liquid crystal molecules.
In the conductive color filter manufacturing method, the content of a compound having the carboxyl group may be 1.5 percent by weight or lower in contrast to 1 percent by weight of the conductive colorant.
In the conductive color filter manufacturing method, the electrodeposition material may contain a light-transmitting conductive high-molecular compound.
In the conductive color filter manufacturing method, the electrolyte may contain supporting salt, which does not exert an influence on electrodeposition characteristics.
The conductive color filter manufacturing method further includes: a step of forming a conductive protective layer on the colored electrodeposition film and the black matrix that contain water by which charges can move, after forming the conductive colored electrodeposition film and the black matrix.
In the conductive color filter manufacturing method, a voltage of 5 V or lower may be used as an electrodeposition potential in the step of forming the conductive colored electrodeposition film.
In the conductive color filter manufacturing method, after the black matrix is formed via a photomask, a colored electrodeposition film of a single color or plural colors may be formed so as to have an area overlapped with the black matrix.
According to further another aspect of the invention, in the conductive color filter manufacturing method, after a colored electrodeposition film of a single color or plural colors is formed via a photomask, a black matrix may be formed so as to have an area overlapped with the colored electrodeposition film.
In the conductive color filter manufacturing method, light irradiation may be performed by an exposure system in which at least an image forming optical member A, a photomask for patterning a substrate on which at least a conductive film and a photoconductive thin film are stacked in this order, an image forming optical member B, and a light source are disposed in this order from the substrate side.
In the conductive color filter manufacturing method, light irradiation may be performed by an exposure system in which at least a mirror reflection optical member, a photomask for patterning a substrate on which at least a conductive film and a photoconductive thin film are stacked in this order, an image forming optical member, and a light source are disposed in this order from the substrate side.
This invention also povides a conductive color filter manufacturing apparatus using the conductive color filter manufacturing method includes: an image forming optical member A; a photomask for patterning a substrate on which at least a conductive film and a photoconductive thin film are stacked in this order; an image forming optical member B; and a light source, the component being disposed in this order from the substrate side.
This invention also provides a conductive color filter manufacturing apparatus using the conductive color filter manufacturing method includes: a mirror reflection optical member; a photomask for patterning a substrate on which at least a conductive film and a photoconductive thin film are stacked in this order; an image forming optical member; and a light source, the component being disposed in this order from the substrate side.
This invention also provides a conductive color filter obtained by the conductive color filter manufacturing method.
This invention also provides a liquid crystal display element wherein the conductive color filter is used as a drive electrode for liquid crystal display.